1. Technical Field
The present disclosure relates to a control technique for suppressing shock during lockup end control in a power transmission system for a vehicle which executes the lockup end control for decreasing control hydraulic pressure to release a lockup clutch.
2. Description of Related Art
Of power transmission systems for a vehicle provided with a transmission, a torque converter (or fluid coupling), and a lockup clutch, a power transmission system for a vehicle which executes lockup end control for decreasing control hydraulic pressure to release the lockup clutch is known. The torque converter (or fluid coupling) is provided between the transmission and a power source. The lockup clutch directly connects an input member and an output member of the torque converter (or fluid coupling) with supply of control hydraulic pressure to a control oil chamber. For example, a power transmission system for a vehicle described in Japanese Patent Application Publication No. 2009-14189 (JP 2009-14189 A) is known. In the power transmission system for a vehicle of JP 2009-14189 A, in the lockup end control (lockup clutch release control), command pressure at the time of the start of lockup end control to be executed next time is corrected by learning based on the difference between an actual time and a target time from when the lockup end control is commanded until the release of the lockup clutch is actually started.